From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bruce Richardson Subject: Re: [PATCH v4 3/5] hash: add fallback to software CRC32 implementation Date: Tue, 18 Nov 2014 17:52:27 +0000 Message-ID: <20141118175226.GC5840@bricha3-MOBL3> References: <1409724351-23786-1-git-send-email-e_zhumabekov@sts.kz> <20141118144138.GB32375@hmsreliant.think-freely.org> <546B607B.9030808@sts.kz> <20141118160005.GC32375@hmsreliant.think-freely.org> <546B7E2D.7050705@sts.kz> <20141118174619.GE32375@hmsreliant.think-freely.org> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Cc: "dev-VfR2kkLFssw@public.gmane.org" To: Neil Horman Return-path: Content-Disposition: inline In-Reply-To: <20141118174619.GE32375-B26myB8xz7F8NnZeBjwnZQMhkBWG/bsMQH7oEaQurus@public.gmane.org> List-Id: patches and discussions about DPDK List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces-VfR2kkLFssw@public.gmane.org Sender: "dev" On Tue, Nov 18, 2014 at 12:46:19PM -0500, Neil Horman wrote: > On Tue, Nov 18, 2014 at 11:13:17PM +0600, Yerden Zhumabekov wrote: > >=20 > > 18.11.2014 22:00, Neil Horman =D0=BF=D0=B8=D1=88=D0=B5=D1=82: > > > On Tue, Nov 18, 2014 at 09:06:35PM +0600, Yerden Zhumabekov wrote: > > >> 18.11.2014 20:41, Neil Horman =D0=BF=D0=B8=D1=88=D0=B5=D1=82: > > >>> On Tue, Nov 18, 2014 at 08:03:40PM +0600, Yerden Zhumabekov wrote= : > > >>>> /** > > >>>> * Use single crc32 instruction to perform a hash on a 4 byte v= alue. > > >>>> + * Fall back to software crc32 implementation in case SSE4.2 is > > >>>> + * not supported > > >>>> * > > >>>> * @param data > > >>>> * Data to perform hash on. > > >>>> @@ -376,11 +413,18 @@ crc32c_2words(uint64_t data, uint32_t init= _val) > > >>>> static inline uint32_t > > >>>> rte_hash_crc_4byte(uint32_t data, uint32_t init_val) > > >>>> { > > >>>> - return _mm_crc32_u32(init_val, data); > > >>>> +#ifdef RTE_MACHINE_CPUFLAG_SSE4_2 > > >>>> + if (likely(crc32_alg =3D=3D CRC32_SSE42)) > > >>>> + return _mm_crc32_u32(init_val, data); > > >>>> +#endif > > >>> you don't really need these ifdefs here anymore given that you ha= ve a > > >>> constructor to do the algorithm selection. In fact you need to r= emove them, in > > >>> the event you build on a system that doesn't support SSE42, but r= un on a system > > >>> that does. > > >> Originally, I thought so as well. I wrote the code without these i= fdefs, > > >> but it didn't compile on my machine which doesn't support SSE4.2. = Error > > >> was triggered by nmmintrin.h which has a check for respective GCC > > >> extension. So I think these ifdefs are indeed required. > > >> > > > You need to edit the makefile so that the compiler gets passed the = option > > > -msse42. That way it will know to emit sse42 instructions. It will= also allow > > > you to remove the ifdef from the include file > >=20 > > In this case, I guess there are two options: > > 1) modify all makefiles which use librte_hash > > 2) move all function bodies from rte_hash_crc.h to separate module, > > leaving prototype definitions there only. > >=20 > > Everybody's up for the second option? :) > >=20 > Crud, you're right, I didn't think about the header inclusion issue. I= s it > worth adding the jump to enable the dynamic hash selection? > Neil Maybe for cases where SSE4.2 is not currently available, i.e. for generic= builds. For builds where we have hardware support confirmed at compile time, just= use the function from the header file. Does that make sense? /Bruce >=20 > > --=20 > > Sincerely, > >=20 > > Yerden Zhumabekov > > State Technical Service > > Astana, KZ > >=20 > >=20 > >=20